Entering Flashtime (& Other Uses)
by star.everlasting
Summary: Caitlin doesn't usually make her own Halloween costumes, but this year, she'll make an exception just to see the look on Barry's face. [Snowbarry Week 2019 Day 3 - Halloween]


WOOHOO!

Can I just- can I just say that this is actually my first time actually writing smut? It is SO ODD. I don't actually know how I managed to do it and make it sound a little less cheesy, but I'm SO SORRY if it does end up sounding a little corny. I will also say that this was the first prompt I worked on for SB week LOLOL. I read the prompt, and then this plot bunny would NOT leave me alone.

Written for Day 3 of Snowbarry Week 2019 - Halloween ;)

**Disclaimer**: I don't own the Flash/DCTV

* * *

**October 2, 7:48 AM**

"You know," Frost began, her too-casual tone immediately setting Caitlin on edge, stilling her hands in the middle of zipping up her skirt. "You should do it."

Caitlin narrowed her eyes, pulling up her zip before she stomped into the bathroom to look into the mirror. Frost's piercing blue eyes appeared then, her blue lips pulled back in a wicked smirk. "Do what?" she replied, her hands coming up to fix her hair in an attempt to distract herself, the flush crawling up her neck a dead giveaway. Sharing a body and a more-or-less open bond with Frost meant Caitlin knew exactly what Frost was talking about- their years of learning to share one body and opening their minds to one another made the connection easier whenever the other person wanted to listen in.

With a twinkle in her eyes, Frost's smirk grew even wider. "The idea you had last night, Caity," she said breezily. "I think you should do it. It would be fun. And," she paused for effect, seeing and sensing the reddening of Caitlin's cheeks as she smothered a chuckle. "I'm _positive_ Flash would appreciate it."

Pursing her lips, Caitlin purposefully smeared on pale pink lip gloss in an effort to annoy her counterpart with her least favorite color, conversation dropped. Frost only laughed, and Caitlin could feel her amusement the entire drive to S.T.A.R. Labs.

**2:51 PM**

Despite Caitlin's very best attempts to stay focused on her work and research on a very rare day where no metas were threatening the lives of the people of Central City, Frost's comment from that morning refused to leave her alone. She could sense her counterpart's mirth at her agitation in the back of her mind, until Caitlin, who was chewing fairly hard on her bottom lip, finally threw her pen down in frustration.

It _was_ a good idea, damnit, she thought furiously, eliciting a new round of laughter from Frost. She marched out of her lab, her heels clacking loudly on the tiled floors toward the Cortex where she knew she would find the one person who could help her in her endeavor. After all, he was the one who designed it in the first place. Caitlin silently thanked whoever was listening that Ralph, Iris, Eddie, and Joe were all out that morning, leaving her and-

"Cisco!" she called out, rounding the corner.

As far as she knew, the engineer hadn't called out like their teammates (which, to be fair, most of them had their own daytime jobs anyway) and wasn't out training with Barry. Said engineer swiveled around in his chair just as Caitlin walked into the Cortex, lollipop in his mouth while he flipped through a rather large packet in his hands.

"Hey, Caitlin!" Cisco garbled around the candy currently occupying most of his mouth, which sounded more like, 'hay, Cai'in.' "Wha' ca' I hel' you wi'?"

Taking a page out of Frost's book, Caitlin let out a breath and leaned casually against the desk next to him, trying her best to appear as nonchalant as possible. It backfired painfully- like she had been suspicious of Frost that morning, he was immediately suspicious of her. "Do you still have the specs and designs for Barry's suit?" she asked, feigning as much innocence as she could muster. "I need to see them."

He looked at her warily, slowly putting the packet in his hands to the side and tapping a few keys on the keyboard in front of him to pull up the files. "Why do you need to see them…?" he asked right back after taking the lollipop out of his mouth with a slurp.

Frost immediately chimed in then, Caitlin's warm brown eyes glazing over to her ice-cold blue. "Research," she replied, smirking before giving control back to Caitlin. If anything, Cisco was even more suspicious as he eyed her.

"Okay…do I want to know?" Evidently, and correctly, he decided that question was the safest course of action. Caitlin bit her lip, trying to control the grin spreading on her face.

"No. And, whatever you do, don't tell Barry."

Her friend raised his eyebrows then, repeating after her uncertainly. "Don't tell Barry?"

By now, her grin had grown to be one of those looks that told Cisco to just stop asking what was on her mind- chances were, he _really_ didn't want to know. He nodded slowly in confirmation. "Don't tell Barry."

* * *

**October 4, 8:57 PM**

Caitlin had decided a long while ago that Barry's hugs were the best hugs, and snuggling with him during a night in after dinner and a movie was quite possibly the best feeling in the world. The two sat in blissful silence in her apartment, watching the credits roll with Barry's fingers gently tracing circles on her arm.

"Hey, Cait?" he suddenly asked. She let out a lazy hum, encouraging him to continue. "Iris and Eddie are throwing a Halloween party at their new loft this year. Want to go?"

Snuggling closer, Caitlin grinned up at him, his green eyes looking at her with a tender warmth that she knew she would never tire of. "Sure, sounds like fun."

They were quiet for another few moments before Barry broke the silence again.

"Cait?"

"Yeah?"

"Are those…scraps of red spandex on your floor?"

* * *

**October 31, 5:23 PM**

"Caitlin!" Barry called from the living room, having been duly warned by Killer Frost, who made an appearance when he stepped into the apartment half an hour ago, to _stay out of the bedroom_. "You ready yet? We still have to grab dinner on the way to Iris and Eddie's!"

"Just a sec!" she yelled back behind the closed door. Sighing in fond exasperation, Barry flopped down onto the couch and flung his arm over the back while his other hand came up to rub at his face. He had opted out of dressing up in a costume, instead throwing on a pair of dark jeans and a black dress shirt, rolling the sleeves up to his elbows to go with the dark colors of Halloween.

"Cait, it's really not that huge of a party. Some people from the precinct, Oliver and Felicity and Digg and Lyla, some of Iris' friends; you know most of the people there, you don't…"

Barry trailed off when Caitlin's bedroom door opened, his jaw immediately dropping as his eyes swept her up and down in shock and appreciation, a recall of their not-an-actual-date at the karaoke bar. She bit her lip at his silence, nervousness and excitement both pulsing within her. "What do you think?"

He opened his mouth to respond, but his mouth and throat were suddenly dry. Caitlin had taken his breath away more times than he could count, but Barry knew nothing in the multiverse could amount to this one moment where his girlfriend stood in front of him in an almost-exact replica of his Flash suit, complete with the lightning bolt logo in front, and was modified to hug each of her curves. The top piece was held together with a zipper in the front down to her gold belt, the belt hiding the seams where her top and her pants met. Her brown locks where tied in a side ponytail over her left shoulder, cowl thrown back like a hood, just the way he did it at the lab.

"W…wow. You…look amazing, Cait," he said hoarsely, still struggling to find his voice. A light blush dusted her cheeks at his compliment, making the long prep time worth it- the spandex itself was hard enough to get into, much less zip everything up and make sure she didn't burst any seams. Spandex also didn't hold up nearly as well as Cisco's reinforced tri-polymer, but as a Halloween costume, she worked with what she had (and if that involved an afternoon or two sticking the homemade suit into one of S.T.A.R. Labs' giant sewing machines, the ones that Cisco used, well).

Caitlin intentionally made the suit a little tighter, partially due to Frost's insistence, the material leaving…not a whole lot to the imagination. She sashayed over to the couch, where Barry stood and put both his hands on her waist, his eyes raking up and down her body.

"Surprised?" she asked cheekily, knowing it was probably the last thing he would have ever expected her to dress up as- the Flash himself.

"Definitely," Barry answered, drawing her close and leaning down to kiss her. One of his arms curled around her waist, pulling her even closer to himself, while his other hand tugged at the hairband in her hair until it came out. He promptly threw the hairband on the floor, running his fingers through her loose curls. Hungrily, he deepened the kiss, the image of her in the suit seared into his brain. Caitlin responded just as enthusiastically, her arms wrapped tight around his neck. She felt his hands travel lower down her body until they were at the back of their thighs, and then Barry hoisted her up until her legs were wrapped around his waist, and she could _definitely_ feel the results of her hard work there in between her legs.

He stumbled backwards until his back hit the edge of the kitchen counter, but by then, Barry was too far gone to care, completely lost and drowning in everything that was Caitlin Snow. His lips traveled from her lips to her neck, lightly nipping at the skin there, and once he found her pulse point, Caitlin let out a low moan, her fingers gripping his hair. His hips ground lightly against her core, covered only by her panties and a thin layer of dark red spandex, and she bit her lip hard to contain a groan.

"You know," Caitlin said, breathing hard. "We're not going to make it to the party if we keep going."

Barry's head immediately snapped up, looking at her with darkened green eyes. "Forget the party."

"But I worked so hard on my Halloween costume!"

She felt the familiar _woosh_ of wind flying by, and then they were no longer standing in her kitchen. Instead, Barry had her on her back in her bed, hovering over her. Caitlin almost giggled when she noticed he had taken the time to turn the lights off in her kitchen and her room, plugging in the string lights she hung around the bedroom.

"I'm sure I can make the effort you put into your costume worth your while, Doctor Snow," he told her earnestly, his smirk completely giving him away.

Caitlin gracefully arched her eyebrows. "Can you now, Mr. Allen?"

Barry's smirk only grew wider as he leaned down to kiss her, slowly and deeply, and she pulled him down to rest on top of her. He broke the kiss only to trail his lips down her neck until he reached the zipper at her collarbone that held the suit together hidden underneath a thin layer of spandex connected to the cowl. Flashing her a mischievous smile, he took the zipper in between his teeth and pulled it down, agonizingly slowly, past the lightning bolt logo on her chest down to her belly button, not yet fully loosening her top. He took a moment, pausing for another appreciative sweep of her body and taking in the blush on her cheeks, the way she bit her bottom lip, and the swell of her breasts, covered mostly by her top on both sides. Finally, he reached up and pulled the zip free, her top falling open to fully expose her torso.

It wasn't the first time Barry had seen her naked, mostly or completely, but he found himself in awe each time. Caitlin reached for him then and he eagerly complied, tightening his grip on her while her fingers crept down to the buttons on his shirt, undoing them as quickly as she could. Once his shirt hung open, she pushed it off his shoulders and Barry tore himself away from her for a brief second to pull off his undershirt and threw it somewhere on the floor before he lowered his mouth down to her breasts, licking her nipple teasingly and then putting it into his mouth. His other hand found hers, twining their fingers together tightly.

Caitlin's eyes closed at the waves of pleasure washing over her, soft mewls escaping her lips when Barry turned his attention to her other breast instead. She could feel the wetness between her legs and let go of his hand, holding his face with both of hers to pull him back up into a hungry kiss. Instinctively, he moved his hands down to her hips, making quick work of her rather flimsy belt and pulled down her spandex pants without lingering like he did with her top. His lips moved down to her neck, taking a few precious seconds to pull his jeans off and kick them off the bed.

"Barry," she moaned when his hands came to rest on the inside of her thighs, fingertips brushing against the hemline of her underwear. "Barry, I'm so-"

She gasped, arching her back when his fingers trailed up against her slit, his thumb pressing against her clit and causing her to let out a loud groan. Caitlin grabbed his wrist, locking eyes with him; she was already so aroused, she didn't want any more foreplay. "Condom. Now."

Barry chuckled at her demanding tone. He hooked his fingers into the side of her panties, and Caitlin wriggling out of them as he pulled them down before she yanked his boxers down his legs and threw them aside. Without wasting time, he used his speed to reach into her bedside drawer, pulling out a foil pack and tearing it open, rolling it onto his firm length. He had felt himself go hard as soon as Caitlin had walked out of the bedroom in her Flash costume, and had only grown harder since.

"Living up to your name, Flash," she teased. He only grinned at her and gave her a short kiss, reaching down between her legs to feel her wetness, easily sliding a finger inside of her. Satisfied at how ready and how wet she was, Barry pulled his finger out and looked into her eyes, waiting for her- not that he had to wait long. Warm brown met molten green, and as soon as Caitlin nodded, he lined himself up her entrance and slowly slid into her warmth. Her head snapped back as her back arched in pleasure, Caitlin biting down hard on her lip as she took him deeper inside.

She could feel each inch of him, and her muscles involuntarily clenched around his length, causing Barry to let out a guttural groan. He pulled out just as slowly as he entered, then snapped his hips forward, catching her by surprise and causing Caitlin to let out a sharp mewl. Breathing heavily, she looked at him with half-lidded eyes. "Faster, Barry," she said breathlessly.

He would not deny her wishes; Barry pulled out and thrusted into her, setting a steady pace. Caitlin's moans turned into pleas with each thrust, and that was when he reached down to her clit, his fingers rubbing circles onto the nub. She let out another loud moan, but was caught off-guard when Barry suddenly pulled her into Flashtime, lightning coursing through her, electrifying her with his touch everywhere he was connected to her. Caitlin screamed, her walls clamping down on him as her orgasm ripped through her. The intense clenching around his length snapped Barry's control clean in half, his orgasm following right at her heels as he pounded into her, burying his face into her neck, before finally slowing and stilling.

Releasing them both from Flashtime, Barry pulled out and just laid on top of her, completely out of breath.

"Worth your while?" He asked a few moments later, shifting to his side and pulling her close to him. Caitlin snuggled in, pressing her forehead into his neck and letting out a happy hum. Suddenly pulling back, she fixed him with an odd look.

"Did you just…pull us into Flashtime while we were having sex?"

Unable to contain himself, Barry laughed, his laughter quickly dwindling into an adorably shy smile. "How was it?"

"Hmmm…" Caitlin's right hand trailed up his arm, then up to brush his bangs out of his eyes. "Formulating a hypothesis. Think I'll need a little more evidence to support it though," she said with a mischievous wink.

With another warm laugh, Barry kissed her again.

**7:38 PM**

Lady cop Iris West-Thawne made her way through the crowd of guests in her living room, carefully balancing the two full glasses in her hands until she finally arrived at the couch where Felicity, dressed as Cleopatra, gratefully accepted one of them and took a generous sip. Iris leaned back into the couch, belatedly clinking glasses with her friend. "What a year," she murmured. Between her journalism work and moonlighting at S.T.A.R. Labs while wedding planning, she desperately needed a break.

"Drinking to that," her friend replied, downing almost all the liquid Iris had just brought her. She twirled the wineglass between her fingers, her gaze straying to Oliver and Eddie on the other side of the room, who were in deep conversation with one of Eddie's friends from the CCPD.

Iris took another sip. "Party started a while ago, and Barry and Caitlin still haven't shown up," she said, glancing at the door. "They told me they'd be here-" she was cut off by Felicity clearing her throat, the woman holding her phone up to her face with a knowing grin.

There was a single text message on the screen:

_Flash and Caity probably won't make it tonight FYI._

It was signed with a snowflake.


End file.
